// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/test/histogram_tester.h"

#include <stddef.h>

#include "base/metrics/histogram.h"
#include "base/metrics/histogram_samples.h"
#include "base/metrics/metrics_hashes.h"
#include "base/metrics/sample_map.h"
#include "base/metrics/statistics_recorder.h"
#include "base/stl_util.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace base {

HistogramTester::HistogramTester()
{
    StatisticsRecorder::Initialize(); // Safe to call multiple times.

    // Record any histogram data that exists when the object is created so it can
    // be subtracted later.
    StatisticsRecorder::Histograms histograms;
    StatisticsRecorder::GetSnapshot(std::string(), &histograms);
    for (size_t i = 0; i < histograms.size(); ++i) {
        histograms_snapshot_[histograms[i]->histogram_name()] = histograms[i]->SnapshotSamples().release();
    }
}

HistogramTester::~HistogramTester()
{
    STLDeleteValues(&histograms_snapshot_);
}

void HistogramTester::ExpectUniqueSample(
    const std::string& name,
    base::HistogramBase::Sample sample,
    base::HistogramBase::Count expected_count) const
{
    base::HistogramBase* histogram = base::StatisticsRecorder::FindHistogram(name);
    EXPECT_NE(static_cast<base::HistogramBase*>(NULL), histogram)
        << "Histogram \"" << name << "\" does not exist.";

    if (histogram) {
        std::unique_ptr<base::HistogramSamples> samples(
            histogram->SnapshotSamples());
        CheckBucketCount(name, sample, expected_count, *samples);
        CheckTotalCount(name, expected_count, *samples);
    }
}

void HistogramTester::ExpectBucketCount(
    const std::string& name,
    base::HistogramBase::Sample sample,
    base::HistogramBase::Count expected_count) const
{
    base::HistogramBase* histogram = base::StatisticsRecorder::FindHistogram(name);
    EXPECT_NE(static_cast<base::HistogramBase*>(NULL), histogram)
        << "Histogram \"" << name << "\" does not exist.";

    if (histogram) {
        std::unique_ptr<base::HistogramSamples> samples(
            histogram->SnapshotSamples());
        CheckBucketCount(name, sample, expected_count, *samples);
    }
}

void HistogramTester::ExpectTotalCount(const std::string& name,
    base::HistogramBase::Count count) const
{
    base::HistogramBase* histogram = base::StatisticsRecorder::FindHistogram(name);
    if (histogram) {
        std::unique_ptr<base::HistogramSamples> samples(
            histogram->SnapshotSamples());
        CheckTotalCount(name, count, *samples);
    } else {
        // No histogram means there were zero samples.
        EXPECT_EQ(count, 0) << "Histogram \"" << name << "\" does not exist.";
    }
}

std::vector<Bucket> HistogramTester::GetAllSamples(
    const std::string& name) const
{
    std::vector<Bucket> samples;
    std::unique_ptr<HistogramSamples> snapshot = GetHistogramSamplesSinceCreation(name);
    if (snapshot) {
        for (auto it = snapshot->Iterator(); !it->Done(); it->Next()) {
            HistogramBase::Sample sample;
            HistogramBase::Count count;
            it->Get(&sample, nullptr, &count);
            samples.push_back(Bucket(sample, count));
        }
    }
    return samples;
}

HistogramTester::CountsMap HistogramTester::GetTotalCountsForPrefix(
    const std::string& query) const
{
    EXPECT_TRUE(query.find('.') != std::string::npos)
        << "|query| ought to contain at least one period, to avoid matching too"
        << " many histograms.";

    // Find matches by using the prefix-matching logic built into GetSnapshot().
    StatisticsRecorder::Histograms query_matches;
    StatisticsRecorder::GetSnapshot(query, &query_matches);

    CountsMap result;
    for (base::HistogramBase* histogram : query_matches) {
        std::unique_ptr<HistogramSamples> new_samples = GetHistogramSamplesSinceCreation(histogram->histogram_name());
        // Omit unchanged histograms from the result.
        if (new_samples->TotalCount()) {
            result[histogram->histogram_name()] = new_samples->TotalCount();
        }
    }
    return result;
}

std::unique_ptr<HistogramSamples>
HistogramTester::GetHistogramSamplesSinceCreation(
    const std::string& histogram_name) const
{
    HistogramBase* histogram = StatisticsRecorder::FindHistogram(histogram_name);
    // Whether the histogram exists or not may not depend on the current test
    // calling this method, but rather on which tests ran before and possibly
    // generated a histogram or not (see http://crbug.com/473689). To provide a
    // response which is independent of the previously run tests, this method
    // creates empty samples in the absence of the histogram, rather than
    // returning null.
    if (!histogram) {
        return std::unique_ptr<HistogramSamples>(
            new SampleMap(HashMetricName(histogram_name)));
    }
    std::unique_ptr<HistogramSamples> named_samples(histogram->SnapshotSamples());
    auto original_samples_it = histograms_snapshot_.find(histogram_name);
    if (original_samples_it != histograms_snapshot_.end())
        named_samples->Subtract(*original_samples_it->second);
    return named_samples;
}

void HistogramTester::CheckBucketCount(
    const std::string& name,
    base::HistogramBase::Sample sample,
    base::HistogramBase::Count expected_count,
    const base::HistogramSamples& samples) const
{
    int actual_count = samples.GetCount(sample);
    std::map<std::string, HistogramSamples*>::const_iterator histogram_data;
    histogram_data = histograms_snapshot_.find(name);
    if (histogram_data != histograms_snapshot_.end())
        actual_count -= histogram_data->second->GetCount(sample);

    EXPECT_EQ(expected_count, actual_count)
        << "Histogram \"" << name
        << "\" does not have the right number of samples (" << expected_count
        << ") in the expected bucket (" << sample << "). It has (" << actual_count
        << ").";
}

void HistogramTester::CheckTotalCount(
    const std::string& name,
    base::HistogramBase::Count expected_count,
    const base::HistogramSamples& samples) const
{
    int actual_count = samples.TotalCount();
    std::map<std::string, HistogramSamples*>::const_iterator histogram_data;
    histogram_data = histograms_snapshot_.find(name);
    if (histogram_data != histograms_snapshot_.end())
        actual_count -= histogram_data->second->TotalCount();

    EXPECT_EQ(expected_count, actual_count)
        << "Histogram \"" << name
        << "\" does not have the right total number of samples ("
        << expected_count << "). It has (" << actual_count << ").";
}

bool Bucket::operator==(const Bucket& other) const
{
    return min == other.min && count == other.count;
}

void PrintTo(const Bucket& bucket, std::ostream* os)
{
    *os << "Bucket " << bucket.min << ": " << bucket.count;
}

} // namespace base
